1. Field of the Invention
The present invention relates, in general, to orthodontic expansion appliances and more specifically to a non-slip orthodontic expansion screw.
2. Information Disclosure Statement
A preliminary patentability search in class 433, subclass 7 and class 411, subclass 914 disclosed the following patents which may be relevant to the present invention: Jedlicka, U.S. Pat. No. 3,022,197, which discloses spreading a siloxane elastomer between the threads of screws, bolts or the like and corresponding threaded receptacles to adhesively bond the parts together so that shocks, vibrations, etc., will not cause loosening of such connections; Anthony, U.S. Pat. No. 3,061,455, which discloses applying a first chemical compound on the threads of a bolt or the like and applying a second chemical compound on the threads of a coacting nut or the like so that when the two parts are screwed together the two compounds will unit by chemical action to oppose the separation of the two parts; Allen et al, U.S. Pat. No. 3,069,387, which discloses a thixotropic thread lubricant for reducing the galling between threaded members of stainless steel, aluminum and the like and employs a relatively high concentration of Teflon; and Tajima, U.S. Pat. No., 4,576,847, which discloses a threaded member made of fiber-reinforced plastic having at least the threaded portions coated with a cross-linked nylon resin to enable the smooth meshing of a nut or the like with a bolt or the like with a coacting threaded member without jolting. Further, the present inventor is aware of Kraus et al, U.S. Pat. No. 4,347,054, which discloses an orthodontic expansion screw. None of the above patents disclose or suggest an orthodontic expansion screw appliance including a first screw body having an internally threaded bore; first retention means attached to the first screw body for attaching the first screw body relative to a first area of the patient's teeth; a second screw body having an internally threaded bore; second retention means attached to the second body for securing the second screw body relative to a second area of the patient's teeth; a screw spindle having an externally threaded first end for being screwed into the internally threaded bore of the first screw body and having an externally threaded second end for being screwed into the internally threaded bore of the second screw body; rotation of the screw spindle causing the first and second screw bodies to move relative to one another; and fill means positioned between the internally threaded bores of the first and second screw bodies and the externally threaded first and second ends of the screw spindle for preventing the externally threaded first and second ends of the screw spindle from inadvertently rotating within the internally threaded bores of the screw bodies.
Additionally, the inventor is aware of a "Scheu" expansion screw in which a threaded plastic sleeve is screwed onto the screw spindle in an attempt to reduce slippage; the "Scheu" expansion screw is used in a removal-type appliance in which the screw is embedded into acrylic for retention to the teeth.
None of the known prior orthodontic expansion appliances, such as the one disclosed by Kraus et al, addresses the problem of slip-back, nor have Teflon threads been used on any type of orthodontic screw appliance in the prior art.
The Jedlicka, Anthony and Tajima patents address the problem of thread slippage primarily by locking the screw threads in fixed positions by use of adhesive-type compounds.
The Allen patent which uses Teflon coatings on screw threads has as its object to lubricate particularly tight fittings in an effort to prevent galling of the threaded parts.